1. Field of the Invention
The present invention relates, generally speaking, to a device designed to monitor parameters characterizing the condition of a battery in view of recharging the battery periodically with a high current and signaling any failure on it.
More especially the invention deals with a storage battery control device comprising means for supplying clock signal pulse having variable frequency in proportion to a battery charge and discharge current, means for estimating an instantaneous capacity of the battery depending on a clock signal pulse up-down count, and means for recharging the battery from a mains or supply voltage as soon as the instantaneous capacity is equal to a first capacity substantially less than a maximum capacity of the battery.
2. Description of the Prior Art
In such a known device, the instantaneous capacity of the battery is estimated directly in proportion to the charge and discharge current. However, the available capacity of the battery is always lower than the capacity of the battery on charge. The ratio of the capacity available to the charged capacity, referred to as efficiency, varies depending on the temperature especially when the battery is on full load, and decreases rapidly when the ambient temperature increases. In particular, the self-discharge current increases all the more when the ambient temperature is high. Thus an estimate of the instantaneous capacity without considering the efficiency and the temperature, underestimates and considerably falsifies the capacity measurement on which the cyclic recharge of the battery depends. Without subjecting the battery to an excessive overload that might damage it, it is also of advantage of recharge the battery to a maximum capacity corresponding to a suitable overload rate.